Method of manufacturing hydrogen peroxid.



f naeasao, '110 Drawing.

commercially obtaining hydrogen peroxicl.

by the distillation of persulfates. In the employment of persulfuric acid for the manufacture of hydrogen peroxid two ways have hitherto been suggested. In the older method, electrolytically prepared solutions of free persulfuric acid are distilled; in the later method as is, for example, disclosed inthe German patent specifications Nos. 241702 and 256148 and also in the Austrian patent specification No. 34775, one proceeds from the persulfates which are decomposed by sulfuric acid and the hydrogen peroxid solutions then either mechanically separated without distillation from the remaining bisulfates or as in the second mentioned patent the resulting hydrogen peroxid obtained by distillation. The older method which commences with free electrolytically prepared persulfuric acid enables very easy continual work and especially a combination of the manufacturing process with the decomposing process of the persulfuric acid to a continuous method. In this case the sulfuric acid to be oxidized can be supplied to one side of the electrolytic cell and the finished persulfuric acid leaving at the other side can be directly supplied to the distilling apparatus from which the remainmg sulfuric acid then returns in a circuit to the electrolytic cell. This method has thus in spite of the drawbacks attached to it (the difficult maintenance of the persulfuric acid) the great advantage of being easily and conveniently carried out commerciall i Tile method of obtaining hydrogen peroxid from'solid persulfate renders the carrying out of a continuous process on a commercial scale considerably more difiicult.

Even the steps in the manufacture of the solid persulfates in the cell makes the carrying out of a continuous combination process almost impossible. In the manufacture of solid persulfates of which only the difli- J'QSEF PATEK, or KARLSHORST, NEAR. BERLIN, Gina t it v I Specification of Letters Patent.

' METHOD OF MANUFACTURING-HYDROGEN PE BOXIIL Patented an ea, ieia.

Application-filed March 4, 1914. Serial No. 822,488.

cultly soluble potassium persulfate has been suggested, the precipitated salt must be from time to timeremoved from the electrolyzer and freed from the adhering sul furic acid by centrifugal action. It has (page 2, line 22 et seq.) to purify the persulfate by recrystallization in order to free it from the inclosed mechanical impurities through whose surface action the resulting hydrogen peroxid would be considerably decomposed, for, as Wolfenstein and others have ascertained, solid bodies, of all kinds act during the distillation of hydrogen peroxid solutions as catalytic agents (Gmelz'n- Kraut, Homolbuck I 1) 7th edition, page 131). This preparation of the potassium persulfate for the decomposition necessitates not only a considerable expenditure of labor, but is also accompanied with oxygen losses during the recrystallization which are not inconsiderable, even .in the case of the difficultly soluble'potassium persulfate, but which would appear to render the more soluble persulfate, such as the ammonium or sodiumpersulfate, entirely unsuitable for this method of manufacturing hydrogen peroxid.

Thus in the manufacture of the dilhcultly soluble potassium persulfate in the cell, as well as in the necessary preparation of the persulfate for the decomposition, there is a practically unavoidable obstacle for a continuous method. 7

While the employment of solid potassium ersulfate or during its decomposition with highlyconcentrated sulfuric acid, mixture rich in oxygen result which can be separated or distilled, nevertheless it must, on the other hand, be remembered that these mixtures rich in oxygen do not of themselves occasion the yield of hydrogen peroxid,

since in addition to the reactions'which'are given in the German atent specification No. 241702 the reactions etween the Caro acid. and the hydrogen peroxid formed according to the equation v H SO +H O =H SO,+H O+2O must also be considered, a reaction which during the. concentrated work, as is pro posed, is of great importance since with the concentration of the sulfuric acid the speed of formation of the Caro acid also increases (Gagwh'n-Kmwtl (1). 7th ed. page. 567 and 569 The inventor has endeavored to solve the problem of obtaining a method which while utilizing persulfates offers the easy operation of the method withfree persulfuric acid, that is, it combines the advantages of both processes, which consists in comm'enc ing with the comparatively stable persulfat es, on the one hand, and creating a continuous circulating process on the other hand. The essential feature of the present, invention consists in commencing withper sulfate solutions instead of solid persul- 1 fates and in the use of the easily soluble'peiw sulfates'instead of the difiicultly soluble perf salts, as the potassium salts. The use of sostudied'the behavior of ammonium persul- 1.

lutions of easily soluble persalts, among which ammonium persulfate is of chief importance, offers in the first place for the continuity of the operation the great advantage that neither during the electrolytic manufacture of the salt, nor during its decomposition, do precipitations of salts of any kind take place and a purification by recrystallization is dispensed with, since the .solid bodies to be removed by this process can be removed by simple filtration.

According to what has been published, esv pecially as to ammonium persulfate, it was to be assumed that this salt owing to its properties would not be suitable for the manufacture of hydrogen peroxid. The very fact that the persulfuricacid ion is loosely combined with the easily oxidizable 7 ammonium group ledfone to assume that this persulfate would behave differently from the more stable persulfates of the fixed alkalis and especially of potassium. In an extensive work Levy and Migliorini have fate in this" direction and have ascertained that the ammonia of the ammonium persulfate solution oxidizes at temperatures between 50 C. and-100 C. for the greater part to nitric acid, immaterial of whether the solutionis neutral, alkaline orslightly" acid (Zentmlblatt "1908, II, page 929). Those skilled in the art would assume there from that the economical utilization 'ofthe ammonium persulfate as the-fundamental material for the manufactureof hydrogen peroxid was without prospect.

It was therefore still more surprising that:

the distillation of. mixtures 'ofammonium persulfatesolutions" and sulfuric acid led to good and even very good yields 'of hydrogen" v peroxid.- The oxygen actively present in the persu'lfate can be almostquantitatively re:

obtained as hydrogen peroxid. The method is. carried out by distilling the mixtures- 'as rap-idly as possible and preferably in a vacuum andtakin hydrogen peroxid is rapidly removed .from' care that the resulting the distilling chamber. It may be left undecided as to the reasons of this apparent contradiction. Itis not improbable that the experimental conditions of Levy and Migliorini were" different and that they 'may have, for example, allowedthemixturessto standfora long time at, the giventemperatures, while the applicant. takes care to rapidly removethe 1 hydrogen" peroxidformed. It is a fact that in the operation described only slight oxidizing of theam- .monia could be observed; It is possible, by the use of easily" soluble ersulfates, particularly ammomum persul ate, to carry out a continuous method of manufacturing hypossible 'withthe free persulfuric acid; I In this case, however, at the same time those drawbacks which resulted in the employ- .mentof free persulfuric acid in the'continuousmethod are obviated. Thus the advantages of the one process are combined with the advantages of the other process -while obviating:- the corresponding disadvantages. v a

An example of my method consists in oxidizing ammonium bisulfate solution in an electrolytic apparatus to ammonium persulfate solution and distilling this with sulfuric acid. The solution of bisulfate thereby remainin is again supplied to the electrolyzer wit out the solid salt being separated as in the case of potassium bisulfate.

As compared with the -old continuous method with the useof free persulfuric acid, the -method with thefformationand decomposition, of ammonium .persulfate" is already insofar more economically advan- 'tageous that, as is known,the manufacture drogen peroxidsuch as was otherwise only of the ammonium persulfate in the cell'is cheapertha'n that of. the free persulfuric acid. While the formationhor the dura- I bility of .the persulfuric {acid in the cell at temperatures-over 10 C. rapidly dimin-- ishes andone must thereforeprovidefor an I energetic coolin inthe manufacture of am- I mon1um persulatethiscostly cooling may 1 be entirely avoided. I As 1 Levy hasascertained, the yield-of ammonium 'persulfate even upto 309 Gris still ,independent of the temperature (Zeits'chrift ffir Elektroclzemz'e 1903, page 427).' Asimple water cooling is thus suflicient to' render the current heat non-dangerous. Thecurrent yield is also very great in the manufacture of ammonium persulfate and can be raised to 80% as compared with 40% of the potassium persulfate and 50% in the case of the persulfuric acid. Moreover, while one in the case of persulfuric acid must Work with dia hragms and employ an electric tension' previous literature apparently entirely unsuitable therefor, is particularly suitable as the commencing material and the more so when it is desired-to produce a continuous method.

I claim:

1. A process for the production of hydrogen peroxid which comprises adding sulfuric acid to a solution of ammonium persulfate and rapidly separating the peroxid of hydrogen from the solution.

.2. A process for the production of hydrogen' peroxid which comprises adding sulfuric acid to a solution of ammonium persulfate and rapidly separating the peroxid of hydrogen from the solution by distillation.

In testimony whereof I have afi'ixed my signature in presence of two witnesses.

JOSEF PATEK.

Witnesses:

WOLDEMAR HAUPT, HENRY HASPER. 

